This invention relates to valves, and more particularly to a self-cleaning hot water solenoid valve such as is used in a hot beverage vendor to control the flow of hot water from the hot water tank of the vendor for a hot beverage (e.g., coffee).
Prior solenoid valves such as used in hot beverage vendors for controlling the flow of hot water from the hot water tank of the vendor are prone to leakage past the valve seat after a relatively short interval of use in the field. It appears that such leakage is due primarily to the accumulation of scale (e.g., calcium sulfate, calcium carbonate, magnesium carbonate, iron carbonate) on the valve seat and the movable valve member, the incrustation of scale preventing the movable valve member from completely sealing against the seat and thereby resulting in water seeping past the seat. The incrustation is increased and hastened by the fact that the water is very hot (e.g., 205.degree.-210.degree. F.) and is especially acute, of course, where the water has a relatively high concentration of dissolved minerals that tend to precipitate when the water is heated to such temperatures.